Unipolar barrier structures based on n-HgCdTe with superlattices as a barrier [Review]

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Abstract
Subject of study. The application of superlattices as barrier layers in unipolar barrier nBn structures based onn-HgCdTe grown by molecular beam epitaxy is studied. Aim of study. The aim is the analysis of the current state of theoretical and experimental research on the creation of unipolar photosensitive barrier nBn structures based on Hg1−x CdxTe grown by molecular beam epitaxy with superlattices as the barrier layer. Method. To achieve the aim, the results of theoretical and experimental studies of the use of superlattices as barrier layers in unipolar barrier nBn structures based on n-HgCdTe grown by molecular beam epitaxy were analyzed. Ab initio modeling of the energy diagram of superlattices in general and superlattices based on HgCdTe in particular is an extremely labor-intensive task. Therefore, the results of similar calculations performed by other authors, as well as the results of experimental studies that verify these calculations, were analyzed for the purpose of assessing the applicability of superlattices as the barrier in HgCdTe nBn structures. The goal was to determine the optimal values of the superlattice parameters based on this analysis. Main results. Based on the analysis of the results of currently known theoretical and experimental works that use superlattices as barriers in nBn structures based on n-HgCdTe, the ranges of optimal values of superlattice parameters (compositions and thicknesses of superlattice barrier layers and quantum wells) were determined. The need for additional research on the protection (passivation) of the side faces during the manufacture of experimental samples in the configuration of mesa structures to minimize the contribution of surface leakage currents to the dark current of the photosensitive structure was also noted. Practical significance. This work was aimed at analyzing the current state of the research in the area under consideration and determining which configurations of superlattice barriers seem to be optimal. As the use of superlattices in barrier nBn structures based on n-HgCdTe is considered to be the most promising way to eliminate the potential barrier for minority charge carriers, the results of this work can form the basis for developing the design of photosensitive structures in the MWIR and LWIR ranges and the subsequent creation of photodetector elements.

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